Being a Japanese actor, Ken'ichi Matsuyama made a breakthrough when portraying L in the 2006 films Death Note, Death Note: The Last Name, which earned him the 2006 Hochi Film Award for Best New Actor and 2007 the Japan Academy Award for Best New Actor and Yokohama Film Festival Award for Best New Talent. Moreover, he received the Takasaki Film Festival award and 64th Mainichi Film Award for Best Actor in 2010.
He began modeling in 2001 and started acting with a small role in the NTV drama Gokusen in the next year. In 2003, he appeared as a supporting role in Bright Future.
On April 1, 2011, he married
Koyuki Katō, who co-starred with him in Kamui Gaiden, with a son (born January 5, 2012) and daughter (born 2013).